AiM MyChron3 Basic - Manual (Page 12)

12
The Optical beacon
The optical Beacon Transmitter has to be placed trackside to mark laps. Ensure
that the infrared receiver eye faces the side of the track where the Beacon has
been placed, otherwise the system will not record lap time.
The Beacon transmitter is powered using 8 AA batteries or an external 12V power
cable. If you are using 8 AA batteries, unscrew the back cover of the Beacon
transmitter and place the battery pack into the transmitter casing.
The transmitter has two operating modes: Low power and High power. The Low
Power Mode can to be used when the track is less than 30 feet / 10 meters wide,
while the High Power mode has to be used when the track is wider than 30 feet /
10 meters.